SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6c68f0165f4b249643452dbb46b7d28c34f549051b267f129d66b81e2540ca2' 
  AND token = 'NOuOntIl19hLpvQFmRwLj7i/FfDhtlW8GfiqSnL7NVs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}